1. Field of the Invention
The present invention relates to a dicyclohexylethylene derivative, and more particularly, to a dicyclohexylethylene derivative as a liquid crystal compound suitable as a component of a display material, and a liquid crystal composition containing said derivative.
2. Description of Related Art
Liquid crystal display devices have been recently introduced, as a new display system, into personal computers, office automation machines and the like, and have gained rapidly in importance.
This is due to the fact that, among many liquid crystal display systems, a supertwisted nematic (STN) system or a supertwisted birefringence effect (SBE) system, and an active matrix system using a thin film transistor (TFT) have been recently used to meet the demand for multicolor display and large picture.
Liquid crystal materials used for these display systems are required to have various properties such as exhibiting a mesomorphic phase at temperatures where the display device is used, stability to environmental factors (moisture, heat, air, light, electricity, etc.) colorlessness, large (or small) anisotropic amount of refractive index (.DELTA.n), large (or small) elastic constant ratio, large anisotropic amount of dielectric constant (.DELTA..epsilon.), low viscosity, high specific resistance, less change of the specific resistance with time, wide d/p (d: cell thickness, p: pitch length) margin and the like.
At present, however, there is no single compound capable of sufficiently driving a display device, and therefore, practically used liquid crystal materials are liquid crystal compositions composed of a mixture of several liquid crystal compounds. Consequently, the liquid crystal compound have to be compatible with other liquid crystal compounds.
In the present specification, liquid crystal compounds mean those capable of contributing to driving liquid crystal display devices at least to some extent.
As an analogue of the compound of the present invention, a compound of the formula, ##STR2## where n is 3,4,5,6 and 7 (Japanese Patent Application Laid-open No. 215336/1986) is known. However, this compound has high viscosity and less compatibility at low temperatures, and has drawbacks that the specific resistance and its change with time prevent use of the compound for TFT.
In addition, the following compounds containing fluorine atoms in the molecule are known as analogues of the compound of the present invention. ##STR3##
In various liquid display systems as well as the above-mentioned liquid display system, wide operation range, rapid response speed, low driving voltage and the like are in demand.